Bring colour to your garden by planting delightful and vibrant summer-flowering bulbs, corms, rhizomes and tubers.
It’s time to plan your summer garden. If you want to plant bulbs for colour, you need to consider your water situation. Planting bulbs in containers is a water-wise option.
What is a bulb?
A bulb is a plant’s underground pantry – a place where nutrients from the roots and foliage are stored for future use. Gardeners use the term “bulb” to cover a number of roots including corms (gladiolus), tubers (begonia), tuberous roots (dahlia), rhizomes (iris) and rhizomatous rootstock (agapanthus).
Corms, tubers and rhizomes can be lifted and stored in a cool and dry place once their foliage has dried.
True bulbs, like lilium, have modified leaves that are swollen, fleshy scales and should not be allowed to dry out.
Time to plant
With soil temperatures warming, summer-flowering bulbs are sending out roots in search of food and moisture to support their summer show.
Look for coloured arums, agapanthus, alstroemeria, tuberous begonia, dahlia, eucomis, galtonia, gladiolus, hippeastrum (amaryllis), liatrus, lilium, tigridia and tuberose.
Where to plant
Grow liliums and tuberoses near windows and doorways where their fragrance can be enjoyed, and in borders among summer-blooming roses and perennials.
For an exotic flower for the summer garden, try Tigridia pavonia, the Mexican shellflower. It is also known as the peacock or tiger flower, referring to the open-faced flowers in red, yellow, pink, purple and orange with contrasting spots. Although individual flowers only last a day, each stalk produces numerous blooms. These are true bulbs and are dormant in winter.
Some of the most beautiful summer-flowering bulbs and tubers are indigenous. Agapanthus are evergreen or deciduous perennials with fleshy, rhizomatous rootstock, good for holding soil on banks. Umbels of white, blue, navy and indigo flowers are held on sturdy stems of varying heights above dark green or variegated strap-like foliage.
Plant en masse, in borders and in water-wise and indigenous gardens. Edge paths, driveways and borders, rockery pockets and pots with miniatures. White agapanthus will stand out in a twilight garden.
Berg hyacinths (Galtonia candicans), with strap-like foliage and tall spikes of fragrant white bell-shaped flowers, add an elegant statement when planted in groups in borders.
White iceberg roses, white-flowered agapanthus and white bellflowers of galtonia will add interest to the evening garden.
Eucomis is a deciduous bulb with wavy-edged leaves and a cylindrical raceme of starry yellow-green flowers, with a topknot of leaves that gives it its everyday name, the pineapple flower. Cultivars have flowers in pink and burgundy shades. Eucomis is suited to rock gardens and in large containers.
Crocosmia (garden montbretia), a member of the iris family, has tall branched stems with spikes of star-shaped orange to red flowers. In Growing Bulbs in Southern Africa, Floris Barnhoorn of Hadeco writes that deeply shaded areas with lots of moisture suit these plants best.
The big three are gladiolus, dahlia and amaryllis.
Tuberous dahlias provide spectacular colour. Flowers vary from tiny pom-poms to large exhibition-type blooms to suit gardens large and small. Insert a sturdy stake at planting time to avoid later damage to tubers and roots.
Given a sunny position, well-composted soil, excellent drainage and regular feeding and (grey) water, they will flower throughout summer and well into autumn.
Inca lilies (Alstroemeria spp), a perennial with tuberous fleshy roots, flowers throughout summer and into autumn. Modern cultivars have large flowers of white pink, red, gold, lavender and cerise. Tall varieties will need staking, or choose a compact cultivar such as A Princess Series. Inca lilies spread and are best given a bed to themselves. Cut flowers last well.
Plant bulbs roughly twice the depth of the diameter of the bulb, spacing large bulbs 10cm to 15cm apart and small bulbs 3-5cm apart.
Plant small bulbs in groups for the best display.
Mark where bulbs are planted by sprinkling a layer of light-coloured sand over the area. This will prevent you from inadvertently digging them up, or piercing the bulbs with a fork.
Feed with a bulb fertiliser as plants start to grow, and after flowering to help bulbs store nutrients.
Mulching is essential for growing bulbs in dry conditions to help conserve moisture. Most actively growing bulbs need watering, on average, every four days.
Depending on the source, grey water can be used, but should not be stored for than 24 hours. Shower and bath water is suitable. If your laundry detergent is biodegradable, this water can also be used.
Plants will benefit from an occasional flushing of tap water to remove any grey water residue.
If you are not able to use potable water, use harvested rain or retained strained vegetable and pasta cooking water to water bulbs.